Many mobile phones can perform an authentication process such as entering a password before providing access to a service or function of a mobile phone. For example, the authentication process may comprise comparing the password to a registered password stored in a memory of the mobile phone. When a user performs the authentication process, password information should not be easily viewed by others. A user generally inputs a password by operating input keys to perform the authentication process, and operation of the input keys by the user may be viewed by others. Thereby, the password may become known to the others.